Abstract: The communication system includes a hybrid fiber/coax distribution network. A head end provides for downstream transmission of telephony and control data in a first frequency bandwidth over the hybrid fiber/coax distribution network and reception of upstream telephony and control data in a second frequency bandwidth over the hybrid fiber/coax distribution network. The head end includes a head end multicarrier modem for modulating at least downstream telephony information on a plurality of orthogonal carriers in the first frequency bandwidth and demodulating at least upstream telephony information modulated on a plurality of orthogonal carriers in the second frequency bandwidth. The head end further includes a controller operatively connected to the head end multicarrier modem for controlling transmission of the downstream telephony information and downstream control data and for controlling receipt of the upstream control data and upstream telephony information.

Abstract: A digitally controlled phase locked loop generates a derived clock signal that is frequency locked to a reference clock signal. The apparatus is comprised of a microcontroller, counter, digital to analog converter (DAC) and a voltage controlled crystal oscillator (VCXO) connected in a feedback loop arrangement. A frequency output derived from the VCXO periodically samples an incoming reference signal. The sampled count value is compared to an ideal count value associated with the same sampling time period. A microcontroller and software-based algorithm perform the phase comparison and loop filter operations of the phase locked loop (PLL).